1. Field of the Invention
The present invention relates to a display apparatus in which a plurality of display device are placed along a front-rear direction corresponding to a viewer's line of sight and which enables three-dimensional viewing of an image by controlling a corresponding image displayed on each display device.
2. Description of the Related Art
Display apparatuses in various forms have been proposed as an apparatus capable of displaying an image having a three-dimensional appearance or such apparatuses have been put to practical use. For example, a liquid crystal shutter spectacles system or the like is well known as a display apparatus capable of displaying an electrically-rewritable image having a three-dimensional appearance. In this liquid crystal shutter spectacles system, pictures of an object are taken in different directions by a camera, image data including parallax information thereby obtained is synthesized into one image signal, and this signal is input to a display device to display images. A viewer wears liquid crystal shutter spectacles. At the times of display of odd fields for example, the liquid crystal shutter corresponding to the right eye is set in a transmitting state while the liquid crystal shutter corresponding to the left eye is set in a light shielding state. On the other hand, at the times of display of even fields, the liquid crystal shutter corresponding to the left eye is set in a transmitting state while the liquid crystal shutter corresponding to the right eye is set in a light shielding state. Images for the right eye and images for the left eye are displayed in the odd fields and in the even fields, respectively, in synchronization with each other. The viewer can recognize an image having a three-dimensional appearance by viewing with the right and left eyes the images for the right and left eyes including a parallax.
A display apparatus is also known in which a plurality of display devices are placed in a front-rear direction on a viewer's line of sight and the viewer views images displayed on the display devices in a state of being superposed on each other as seen from the viewer. These images are discrete in the depth direction but perceivable as an image having a three-dimensional appearance. Another display apparatus is also known which is designed to improve the above-described discrete state in such a manner that the luminances of images respectively displayed on the display devices are changed relative to each other so that the resulting image can be perceived as if the object exists at an intermediate position between the discrete positions. This display apparatus can display an image improved in three-dimensional appearance. For example, a luminance modulation type of display apparatus which displays object images from a plurality of display devices in a superposed state by using a plurality of half mirrors to enable such a display that a semitransparent object is displayed or an object at the back of a foreground object is seen through the foreground object is proposed (see, for example, Patent Document 1).
[Patent Document 1]
Japanese Patent Laid-Open No. 2000-115812
The display apparatus having a plurality of display devices placed in a front-rear direction on a viewer's line of sight has a technical problem in that whether or not an image having a three-dimensional appearance can be easily displayed or whether such an image can be displayed or cannot be displayed depends on the spacing between the display devices.